The overall objective of this project is to understand the structure, function, and physiology of the glycoprotein hormones: thyrotropin, luteinizing hormone, follicle stimulating hormone, and chorionic gonadotropin. Recent research developments include the following: deduction from evidence obtained by the study of patients with choriocarcinoma that the thyrotropic activity of the chorionic gonadotropin molecule mediates hyperthyroidism, demonstration that desialylation of chorionic gonadotropin creates a pure competitive antagonist, while treatment with carboxypeptidase creates an improved agonist of thyrotropin action, and characterization of the kinetic parameters and metabolic products of chorionic gonadotropin metabolism. Future investigations will emphasize the development of clinically applicable methodology to measure the glycoprotein hormones and their metabolites, and characterization of the heterogeneous forms associated with various diseases.